Guess Whose Rock Hard Ab Crack!

Can you guess which sexy star put her rockin' crack on full display in this eye-popping photo?

This celebrity fitness trainer has no shame in her "fit gurl" game ... The shredded star recently took her body goals to her 1 million Instagram followers -- donning this tropical two-piece.

Showin' off her fit physique, this fitness queen -- who notoriously changed Kim Kardashian's bod with her intense workout regime -- modeled several angles of her washboard abs!